Geologic Puzzles: Morrison Formation

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Summary

Outcrop images (faulted strata, interbedded shale and limestone beds that have been tilted, beach rocks of different lithologies) can be used to bring the field into the geoscience classroom, giving students practice in doing what geoscientists do when they are in the field. These particular images are examples of interesting geologic puzzles.

Learning Goals

These images give students opportunities to practice interpreting the geologic history of an outcrop or other feature by having them

make observations

present interpretations based on their observations and on their prior knowledge

pose questions for further information

Context for Use

These images can be used in both small and large classes in various think-pair-share formats, with times ranging from five to twenty minutes per image. These images have been used in historical geology courses and could be used in other geoscience courses.

Teaching Materials

Fault with Morrison Formation on left side of image and Entrada Formation overlain by Morrison Formation on right side. Photo courtesy of Heather Macdonald

Potential Questions

Are these igneous, metamorphic, or sedimentary rocks?

Are the layers continuous across the outcrop?

Can you identify any unit that is present on both sides of the image?

How can you explain this?

What type of fault is shown in this image?

If you could get closer to the outcrop, what you look for?

Teaching Notes and Tips

One approach for using these images would be to have students discuss the image with their neighbor, asking them what do you see and what does it mean. To emphasize observations and to provide more structure, you could ask the students to

make a simple sketch and/or a list of their observations

make an initial interpretation

share their ideas with another student

list questions they would want answered to be able to make a better interpretation or to evaluate alternate interpretations

In either case, after a few minutes, call for responses from students. You might do this using a using a think-pair-share format. Be prepared for a range of responses including ones you might not anticipate. Student answers provide useful insight into their observational skills and thought processes.

The potential questions given below with each image are examples of questions to use as follow-up questions after students give their initial responses or could be a series of directed questions if you don't use a think-pair-share structure.

Assessment

This activity includes informal assessment of the class. You could also collect the sketches and or lists of observations and interpretation(s).